Male Reproductive Organ Weight: Criteria for Detection of Androstenone-Positive Carcasses in Immunocastrated and Entire Male Pigs

SIMPLE SUMMARY: Alternatives to surgical castration of piglets present a challenge for control of boar taint. In this study, the proportion of animals with androstenone levels above the risk threshold for boar taint (>0.5 µg/g fat) was found to be less than 5% in immunocastrated animals (ICs), and testicular weight was a reliable indicator of androstenone-positive carcasses. In contrast, in the entire males (EMs), the proportion of animals with androstenone levels above the risk threshold was much higher (approximately 80%), and the difference in testicular size between EMs with androstenone levels below and above the risk threshold was less pronounced. However, the pelvic urogenital tract weight was reliable in these animals. We thus propose that pelvic urogenital tract and testes weights may be considered a simple, reliable, and time- as well as cost-efficient morphometric indicator for the identification of androstenone-positive carcasses for both ICs and EMs at the slaughter line. ABSTRACT: Immunocastration and rearing of entire males (EMs) are sustainable alternatives to surgical castration. However, these animal carcasses have variable risk of boar taint and should be identified at the slaughter line. We aimed to identify a simple and reliable indicator of androstenone-related boar taint by evaluating pelvic urogenital tract weight as a marker of boar-taint animals at the slaughter line. The pelvic urogenital tract, testes, and accessory sex glands of EMs and immunocastrates (ICs) were collected, dissected, and weighed, before colorimetric measurements of testicular tissue. Additionally, GnRH antibody titers and testosterone, androstenone, and skatole levels were determined. Our results showed that 81.8% of EMs had androstenone levels above the risk threshold (>0.5 µg/g fat; EM/A(high) subgroup), whereas in ICs, the C/A(high) subgroup with androstenone >0.5 µg/g fat accounted for only 4.3%. Androstenone levels correlated negatively with GnRH antibody titers and positively with testosterone levels and reproductive organ weights. Identification of ICs with androstenone levels above the threshold (IC/A(high) subgroup) may be achieved via testes or pelvic urogenital tract weight measurements. However, in EMs, the latter is a more reliable parameter. A principal component analysis based on these variables and hierarchical clustering also distinguished the A(high) from the A(low) subgroup, irrespective of IC/EM. The findings highlight the possible use of pelvic urogenital tract weight along with testes weight as a simple, reliable, and efficient morphometric indicator for identifying androstenone-positive carcasses of different sex categories.